延时摄影因可靠、高效和低成本的优势,在冰川监测中应用广泛,特别是对于获取冰川表面连续变化信息而言。本文基于2020年3月—2021年9月物候相机拍摄的梅里雪山明永冰川末端照片及多期无人机影像,利用地面摄影测量技术和互相关算法,提取...延时摄影因可靠、高效和低成本的优势,在冰川监测中应用广泛,特别是对于获取冰川表面连续变化信息而言。本文基于2020年3月—2021年9月物候相机拍摄的梅里雪山明永冰川末端照片及多期无人机影像,利用地面摄影测量技术和互相关算法,提取了日尺度冰川表面运动速度。结果表明:通过物候图像获取的冰川表面运动速度分辨率高,从海拔2 880~3 150 m a. s. l.,冰川总位移介于(129.38±7.76)~(669.95±247.88) m,年均表面运动速度达(79.14±4.74)~(412.86±152.75) m·a-1,呈从中间向两侧减缓的空间分布特征。冰川表面运动速度随季节变化,夏季流速[(0.13±0.06)~(1.99±0.37) m·d-1]快于冬季流速[(0.07±0.06)~(1.35±0.37) m·d-1]。与冬季流速相比,夏季流速受降水和气温升高的影响不稳定。根据流速分离结果,明永冰川末端底部全年处于融化或压融状态,底部滑动对冰川表面运动速度的贡献介于76%~93%。冬季底部滑动占表面流速高达82%,夏季底部滑动对冰川运动起绝对主导作用。本文采用的技术为进一步研究季风海洋型冰川的运动机制提供了参考方案。展开更多
It has been long known that thermal imaging may be used to detect stress(e.g.water and nutrient deficiency)in growing crops.Developments in microbolometer thermal cameras,such as the introduction of imaging arrays tha...It has been long known that thermal imaging may be used to detect stress(e.g.water and nutrient deficiency)in growing crops.Developments in microbolometer thermal cameras,such as the introduction of imaging arrays that may operate without costly active temperature stabilization,have vitalized the interest in thermal imaging for crop measurements.This study focused on the challenges occurring when temperature stabilization was omitted,including the effects of focal-plane-array(FPA)temperature,camera settings and the environment in which the measurements were performed.Further,the models for providing thermal response from an analog LWIR video signal(typical output from low-cost microbolometer thermal cameras)were designed and tested.Finally,the challenges which typically occur under practical use of thermal imaging of crops were illustrated and discussed,by means of three cereal showcases,including proximal and remotely based(UAV)data acquisition.The results showed that changing FPA temperature greatly affected the measurements,and that wind and irradiance also appeared to affect the temperature dynamics considerably.Further,it is found that adequate settings of camera gain and offset were crucial for obtaining a reliable result.The model which was considered best in terms of transforming video signals into thermal response data included information on camera FPA temperature,and was based on a priori calibrations using a black-body radiation source under controlled conditions.Very good calibration(r^(2)>0.99,RMSE=0.32℃,n=96)was obtained for a target temperature range of 15-35℃,covering typical daytime crop temperatures in the growing season.However,the three showcases illustrated,that under practical conditions,more factors than FPA temperature may need to be corrected for.In conclusion,this study shows that thermal data acquisition by means of an analog,uncooled thermal camera may represent a possible,cost-efficient method for the detection of crop stress,but appropriate corrections of disturbing factors are 展开更多
A difficult problem in forestry is tree inventory.In this study, a GoProHero attached to a small unmanned aerial vehicle was used to capture images of a small area covered by pinus pinea trees. Then, a digital surface...A difficult problem in forestry is tree inventory.In this study, a GoProHero attached to a small unmanned aerial vehicle was used to capture images of a small area covered by pinus pinea trees. Then, a digital surface model was generated with image matching. The elevation model representing the terrain surface, a ‘digital terrain model’,was extracted from the digital surface model using morphological filtering. Individual trees were extracted by analyzing elevation flow on the digital elevation model because the elevation reached the highest value on the tree peaks compared to the neighborhood elevation pixels. The quality of the results was assessed by comparison with reference data for correctness of the estimated number of trees. The tree heights were calculated and evaluated with ground truth dataset. The results showed 80% correctness and 90% completeness.展开更多
文摘延时摄影因可靠、高效和低成本的优势,在冰川监测中应用广泛,特别是对于获取冰川表面连续变化信息而言。本文基于2020年3月—2021年9月物候相机拍摄的梅里雪山明永冰川末端照片及多期无人机影像,利用地面摄影测量技术和互相关算法,提取了日尺度冰川表面运动速度。结果表明:通过物候图像获取的冰川表面运动速度分辨率高,从海拔2 880~3 150 m a. s. l.,冰川总位移介于(129.38±7.76)~(669.95±247.88) m,年均表面运动速度达(79.14±4.74)~(412.86±152.75) m·a-1,呈从中间向两侧减缓的空间分布特征。冰川表面运动速度随季节变化,夏季流速[(0.13±0.06)~(1.99±0.37) m·d-1]快于冬季流速[(0.07±0.06)~(1.35±0.37) m·d-1]。与冬季流速相比,夏季流速受降水和气温升高的影响不稳定。根据流速分离结果,明永冰川末端底部全年处于融化或压融状态,底部滑动对冰川表面运动速度的贡献介于76%~93%。冬季底部滑动占表面流速高达82%,夏季底部滑动对冰川运动起绝对主导作用。本文采用的技术为进一步研究季风海洋型冰川的运动机制提供了参考方案。
基金funded by the Research Council of Norway(Program:"Bionær")。
文摘It has been long known that thermal imaging may be used to detect stress(e.g.water and nutrient deficiency)in growing crops.Developments in microbolometer thermal cameras,such as the introduction of imaging arrays that may operate without costly active temperature stabilization,have vitalized the interest in thermal imaging for crop measurements.This study focused on the challenges occurring when temperature stabilization was omitted,including the effects of focal-plane-array(FPA)temperature,camera settings and the environment in which the measurements were performed.Further,the models for providing thermal response from an analog LWIR video signal(typical output from low-cost microbolometer thermal cameras)were designed and tested.Finally,the challenges which typically occur under practical use of thermal imaging of crops were illustrated and discussed,by means of three cereal showcases,including proximal and remotely based(UAV)data acquisition.The results showed that changing FPA temperature greatly affected the measurements,and that wind and irradiance also appeared to affect the temperature dynamics considerably.Further,it is found that adequate settings of camera gain and offset were crucial for obtaining a reliable result.The model which was considered best in terms of transforming video signals into thermal response data included information on camera FPA temperature,and was based on a priori calibrations using a black-body radiation source under controlled conditions.Very good calibration(r^(2)>0.99,RMSE=0.32℃,n=96)was obtained for a target temperature range of 15-35℃,covering typical daytime crop temperatures in the growing season.However,the three showcases illustrated,that under practical conditions,more factors than FPA temperature may need to be corrected for.In conclusion,this study shows that thermal data acquisition by means of an analog,uncooled thermal camera may represent a possible,cost-efficient method for the detection of crop stress,but appropriate corrections of disturbing factors are
基金financially supported by the scientific research projects coordination unit of Akdeniz University,Project No.FBA-2015-446
文摘A difficult problem in forestry is tree inventory.In this study, a GoProHero attached to a small unmanned aerial vehicle was used to capture images of a small area covered by pinus pinea trees. Then, a digital surface model was generated with image matching. The elevation model representing the terrain surface, a ‘digital terrain model’,was extracted from the digital surface model using morphological filtering. Individual trees were extracted by analyzing elevation flow on the digital elevation model because the elevation reached the highest value on the tree peaks compared to the neighborhood elevation pixels. The quality of the results was assessed by comparison with reference data for correctness of the estimated number of trees. The tree heights were calculated and evaluated with ground truth dataset. The results showed 80% correctness and 90% completeness.
